docs: def invite(self, users, role, expiration=1440):
          """
          A group administrator can invite users to join their group using
          the Invite to Group operation. This creates a new user invitation,
          which the users accept or decline. The role of the user and the
          invitation expiration date can be set in the invitation.
          A notification is created for the user indicating that they were
          invited to join the group. Available only to authenticated users.
  
          Inputs:
             users - A comma separated list of usernames to be invited to the
                     group. If a user is already a member of the group or an
                     invitation has already been sent, the call still returns
                     a success.
                     Example: users=regularusername1,regularusername2
             role	- Allows administrators to set the user's role in the group
                    Roles are:
                       group_member: Ability to view and share items with
                                     group.
                       group_admin: In addition to viewing and sharing items,
                                    the group_admin has the same capabilities
                                    as the group owner-invite users to the
                                    group, accept or decline group
                                    applications, delete content, and remove
                                    users.
             expiration - Expiration date on the invitation can be set for
                          one day, three days, one week, or two weeks, in
                          minutes. Default is 1440
          """
          params = {
              "f" : "json",
              "users" : users,
              "role" : role,
              "expiration" : expiration
          }
          return self._post(url=self._url + "/invite",
                               securityHandler=self._securityHandler,
                               param_dict=params,
                               proxy_url=self._proxy_url,
                               proxy_port=self._proxy_port)